U80 console trouble

Today (well, 2013-02-05 - yesterday, by now, in this timezone) I tried
to run NetBSD/sparc64 on an Ultra 80.  I burnt boot CDs for both my
mutant 4.0.1 (built on an E220r) and stock 5.2 (the 5.2 distribution
install CD image from ftp.netbsd.org).

The machine was finicky about booting from its DVD drive, but I managed
to get each disc to boot.  Trouble was, when it prompted for the
keyboard type after booting, it didn't accept input.

The keyboard was working, and keystrokes were getting to the kernel,
because L1-A dropped into ddb, and keyboard input worked fine in ddb.
But after telling ddb to continue, userland still wasn't responding.

That both 4.0.1 and 5.2 exhibited identical trouble leads me to suspect
it's something systemic.  But I have no idea what it could be.  Anyone
have any thoughts?  I could probably track this down, given time,
motivation, and sufficient access to the hardware.  I don't really have
any of those at the moment, though. :(

If I've left out information that's likely to be relevant, just ask.  I
have access to the hardware in that I can burn a test CD and take it
over there, but that takes arranging an appointment and a trip a
significant distance across the city; it's not something I can do on
short notice or with fast turnaround.

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